Receiver with automatic tuning



July 29, 1941. H. RINIA 2,251,068

RECEIVER WITH AUTOMATIC TUNING Filed June 24, 1939 INVENTOR.

ATTORNEY.

Patented July 29, 1941 UNlTED STATES PATENT OFFICE mesne assignments, to Radio Corporation of America, New York, N. Y., a corporation of Delaware Application June 24, 1939, Serial No. 281,025 In the Netherlands July 14, 1938 6 Claims.

Such a transmission mechanism makes the apparatus more expensive and more bulky and requires high precision construction.

The invention has for one of its objects to permit the use of a very simple transmission mechanism between the push buttons and the tuning means.

According to the invention, for this purpose the automatic tuning of one or more oscillatory circuits is efiected by the displacement of a ferro-magnetic body in the field of a self-indu'ction coil connected in the oscillatory circuit concerned. According to one convenient embodiment of the invention, a rectilinear movement of a push-button is converted into a rectilinear movement of one 01' more iron cores which are each arranged in the self-induction coil of an oscillatory circuit.

It has been found that for the sake of easy tuning the stroke of the push buttons must not be taken too large so that when the iron cores are directly actuated by the push buttons the maximum distance over which the iron cores are movable preferably is about mms. at the most.

The proportion of the maximum self induc ance to the minimum self-inductance is with iron core coils generally comparatively slight and such is more particularly the case with such a slight displacement of the iron cores in the inductance coils.

If a small stroke of the iron cores is utilized it, therefore, becomes diflicult to receive the whole of the intermediate wave range from 200 to 600 ms. without switching over.

In this case it is advisable to divide the wave range to be received into a number of bands of frequencies with which the ratio between the highest and the lowest frequencies of each band is about 2 at the most, which bands may be selected with the aid of a wavelength switch, The

intermediate wave range may be divided, for example, into two or more portions.

This wavelength switch, for example, permits the switch of an additional condenser in parallel with the oscillatory circuit.

It is also possible for the inductance coil of the oscillatory circuit to comprise two windings which may be connected either in series or in parallel with one another.

It is not essential for the invention whether the condenser or the inductance coil is switchedover. Switching over the condenser is a little simpler than switching over the inductance coil. The impedance of the circuit depends, however, on the capacity of the condenser so that when switching over the inductance coil the impedance of the circuit remains substantially constant from one range to another.

For simplicity of manipulation one or more push buttons are preferably mechanically coupled with the wavelength switch in such manner that upon pressing in the push button considered the wavelength range desired is automatically selected.

The coupling between a push button and the wavelength switch may be made either fixed or adjustable.

If means are provided for adjusting each of the push buttons at will to any one of the positions of the Wavelength switch, an appreciably greater choice of stations is possible.

The invention will be explained more fully with reference to the accompanying drawing which represents, by way of example, one embodiment thereof. In said drawing:

Fig. 1 represents a portion of a radio receiver which comprises a plurality of push buttons which each correspond to a predetermined station and of which only one, denoted by I, is shown in the figure;

Fig. 2 is a section through the guiding cylinder of the push button I at the line AB; and Figures 3A, 3B, and 3C are circuit diagrams which illustrate certain possible connections of the wave band switch shown in Figure 1.

In automatically tuning to a station adjusted beforehand, for example the push button 1 is pressed in. A plate 6 common to all the push buttons is thus displaced against the action of a spring which is not shown in the drawing, by a pin 8 which is secured, by means of a screw thread, in the push button I. The plate 6 has secured to it a rod 5 on which are mounted the iron cores of the inductance coils of the oscillatory circuits which are to be tuned. One of these cores, which is denoted by 4, moves, owing to the displacement of the plate 6, into a coil cylinder 3 on which two windings I and 2 are provided. The self-induction of these windings depends on the position of the iron core 4.

Jointly with the condenser 9, the two windings I and 2 form an oscillatory circuit which may be tuned to various wavelength ranges with the aid of a switch III.

The switch I has three positions in which, respectively, for the long wave range the two windings I and 2 connected in series are connected in parallel with the condenser 9, for the one por-- tion of the intermediate wave range the two windings I and 2 are connected in parallel with the condenser 9 and for the other portion of the intermediate wave range the two windings I and 2, together with a condenser H, are connected in parallel with the condenser 9.

The wave length switch It] consists of a stator I2 and a rotor I3 and is shown in the figure in its intermediate position. The stator has two groups of three contacts I4, I5, I8 and IT, IS, IS. The contacts I 4 and I! are connected to one another whilst the condenser II is connected between the contacts l5 and IS. The contact I5 is connected, by means of a conductor 26, to one of the terminals of the condenser 9 and to one of the terminals of the winding I. The contact I9 is connected, through the intermediary of a conductor 2|, to the other terminal of the condenser 9 and to one of the terminals of the winding 2. Those ends of the windings I and 2 which are not connected to the condenser 9 are connected to the rotor contacts 24-25 and 22-23 respectively by conductors 2E and 2i respectively. The circuit arrangement is such that the fields of the windings I and 2 support one another.

The switch I8 may be removed from its intermediate position by either of two electromagnets 26 and 27 which, upon being excited, draw a piece of soft iron 28 which is secured to the rotor I 3 either to the left or to the right. As soon as the switch has been removed from its middle position to a sufficient extent to be enabled to snap into the next switch position, the contact 29 is interrupted with the result that the magnet coil switched into circuit becomes without current. The exciting current which is taken from a source of voltage located between the terminals 30 and 3| may be switched-on by the push button with the aid of which tuning to the desired station is effected. To that end the metallic cap 32 of the push-button 1 contains a rod 33 which is resiliently slidable in the longitudinal direction in a guiding cylinder 34 whilst a projecting rim 35 prevents it from falling out. The contacts 36 and 3! with which this red can establish an electric connection are located in saw-notches in the guiding cylinder of the push-button 'I. This is also distinctly shown in Fig. 2 which represents a section through the said cylinder at the line AB in Fig. 1.

As shown in Figure 1, the cap 32 is connected to ground G through push button I. The same is true of terminal 3!. Cap 32 is constructed so that it may be placed in four different positions by rotation of the same with respect to the frame. Preferably the arrangement is such as to permit four positions which differ from one another by 90". In the position shown the contact 31 will be connected to ground G through rod 33 when push button I is depressed thereby energizing magnet 2'! through the following circuit: grounded contact 31, conductor 31, winding of magnet 2?, switch 29, arm 28, conductor 36, terminal 3c, source of current (not shown) connected between terminals 30 and BI, terminal 3| and ground G. Energization of the magnet 27 causes the rotor I3 to be rotated counterclockwise due to the pull of magnet 2'! on arm 28 thereby connecting windings I and 2 in series with each other and with condenser 9 as shown in Figure 3B. In this case-the condenser II is shorted. If the cap 32 is rotated either or 270 from the position shown, the rod 33 will not come in contact with either one of the contacts 36 or 3'! when push button 'I is depressed. Hence the rotor I3 will remain in the position shown; namely, the middle position, wherein the coils I and 2 and condensers 5 and I: are related as shown in Figure 3A.

If cap 32 is rotated 180 from the position shown in the drawing, then upon depression of push button "I, rod 33 will connect contact 36 to ground. In this case magnet 26 will be energized through the following circuit: grounded contact 35, conductor 35, winding of magnet 36, contact 29, arm 28, conductor 36', terminal 35, source of current (not shown) connected between terminals 39 and 3 I, terminal 31 and ground G. Upon energization of magnet 26, the rotor I3 will be rotated clockwise thereby relating coils I and 2 and condenser 8,as shown in Figure 3C,

After being pressed in the button is retained by a locking device 38 which is drawn to the right by a spring 39. This lock has a fork 40 of which two teeth at and 42 may engage two extensions 43 and 44 provided on the rotor I3 of the switch IS. Now in tuning to a station we press in a push button the conical portion of which displaces the lock 33 to the left. If required, the fork it! forces the switch I0 back into the middle position and at the same time one of the magnets 25 and 2'! may be energized owing to which the switch I8 may receive a bias either to the left or to the right. As soon as the push button has been pressed in to such an extent that the lock is enabled to snap in, the switch turns in this case to the position desired. With the aid of a screw driver the pin 8 may be screwed to and fro so that in the wavelength range selected with the aid of the cap a station may be adjusted. When the cap has a position such that the rod 33 does not make contact with either or 31 the switch It] remains in its middle position.

In the embodiment shown, by way of example, in the drawing there is shown a direct transmission between the push button and the iron cores. It is also possible, however, to effectuate this transmission with the aid of levers. In this case the preadjustment of the iron cores to a predetermined station is, preferably efiected at the place of the cores since thus greater accuracy is generally obtained than in the case of preadjustment at the place of the push buttons.

I claim:

1. In signalling apparatus adapted to be automatically tuned substantially to any frequency within any one of a plurality of wave bands, an adjustable tuning means, a selectively operable device acting upon operation to adjust the tuning means to a predetermined position, operable means coupled for operation with said selectively operable device, said operable means being independently settable to any one of a plurality of different positions, operable wave band switching means which when in one position adjust the radio receiver for operation within one of said wave bands and when in another position adjust the radio receiver for operation within another of said wave bands and when in still another position adjust the receiver for operation within a third wave band, means controlled by said selectively operable device and said independently settable operable means when set to one of its positions and acting upon operation of said selectively operable device for first placin the switching means in a predetermined one of its positions at the time of operating the selectively operable device and thereafter causing the switching means to assume one of its other positions.

2. The arrangement described in claim 1 wherein said selectively operable device comprises a member adjustable with respect to the tuning means whereby the position which the tuning means assumes upon operation of said selectively operable device may be adjustably predetermined.

3. The arrangement described in claim 1 wherein the settable operable means when set to another of its positions acts together with said selectively operable device and upon operation of said device to first place the switching means in said predetermined position provided the switching means is in some other one of its positions at the time of operation of the selectively operable device and thereafter cause the switching means to assume the other of its positions.

4. The arrangement described in claim 1 wherein said settable means when set to another one of its positions is rendered inoperative to control said switching means irrespective of the operation of said selectively operable device, said selectively operable device acting upon operation to cause the switching means to assume said predetermined position provided the switching means is in any other of its positions at the time of operation of the selectively operable device.

5. In a tunable radio receiver which is provided with a push button tuning instrumentality and a wave band change-over switch for adjusting the receiver to tune over any one of a plurality of wave bands, at least one of the push buttons of said tuning instrumentality being rotatable about its axis to various angular positions, means connected with said push button for controlling the operation of said change-over switch upon depression of the push button, said means being arranged so as to operate the change-over switch to adjust the receiver for reception of signals in one of said wave bands upon depression of said push button when said push button is in one of its angular positions and to operate the change-over switch for reception of signals in another wave band upon depression of said push button when said push button is adjusted to another of its angular positions.

6. In signalling apparatus, a variable tuning means, selectively operable push button devices acting upon selective operation thereof to adjust the tuning means to different predetermined positions, a wave-band change-over switching means for adjusting the signalling apparatus for operation within any one of a plurality of different wave bands, at least one of said push button devices being provided with means adjustable to different positions and operative upon depression of said push button device for controlling the operation of said change-over switch, said adjustable means acting to operate the changeover switch to adjust the signalling apparatus for operation in one of said Wave bands upon operation of said push button device when said adjustable means is in a predetermined one of its positions and to operate the change-over switch to adjust the signalling apparatus for operation within another one of said wave bands upon operation of said push button device when said adjustable device is in another one of its positions.

HERRE RINIA. 

